Pressure casting machine having a hydraulically loadable shot unit



May 16, 1967 U. EGGENBEZRGER PRESSURE CASTING MACHINE HAVING A HYDRAULICALLY Filed May 5, 1965 LOADABLE SHOT UNIT 2 Sheets-Sheet l INVE NTUR ULRICH EGGENBERGER MMW y 1967 u. EGGENBERGER 3,319,701

' PRESSURE CASTING MACHINE HAVING A HYDRAULICALLY LOADABLE SHOT UNIT Filed May 5, 1965 2 Sheets-Sheet 2 INVEA/TOR ULRICH EGGENBERER .37 MM q/W W United States Patent 3,319,701 PRESSURE CASTING MACHINE HAVING A HYDRAULICALLY LOADABLE SHOT UNIT Ulrich Eggenherger, @heruzwil, Saint Gall, Switzerland, assignor to Gehrueder Euehler, Uzwil, Switzerland Filed May 5, 1965, Ser. No. 453,290 Claims priority, application Switzerland, May 13, 1964, 6,215/64 3 Claims. (Cl. 164315) which must be stopped suddenly on the compacted melt which is distributed in the mold and in the feed head. It has been known to employ elastic shock absorbers with such apparatus. These proved favorable to break the peak shock loads, but they generally have a sluggish response. It can be established that the remedy is not primarily an elastic absorption of the shock, but that the kinetic energy which accumulates in the shot unit during the shot must be sharply reduced.

In accordance with the present invention, the elements of the shot unit are constructed in a manner permitting control of the maximum shock amplitude by reducing such amplitude. This is done by reducing the masses of the shot pistons and the hydraulic pressure medium actuating the shot pistons, which act as accumulators of kinetic energy. In a preferred arrangement, in accordance with the invention, the pressure casting machine includes a piston accumulator and hydraulic shot unit which are arranged closely adjacent and, in addition, the piston of the piston accumulator and the majority of movable parts of the shot unit are made of light metal material.

Accordingly, it is an object of the invention to provide a pressure molding device which includes a shot piston which is operated from a fluid pressure source, which includes an accumulator arranged adjacent the shot piston and, wherein the parts of the unit, particularly the movable parts, are made of light weight material.

A further object of the invention is to provide a pressure casting device which is simple in design, rugged in construction and economical to manufacture The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

In the drawings:

FIG. 1 is a somewhat schematic partial elevational and partial sectional view of a pressure molding device constructed in accordance with the invention;

FIG. 2 is an enlarged partial fragmentary sectional view of a portion of the mechanism indicated in FIG. 1; and

FIG. 3 is a fragmentary sectional view of the operating portion of another embodiment of a pressure casting machine.

Referring to the drawings, in particular, the invention embodied therein comprises, a pressure casting machine generally designated 100, which includes a horizontally elongated pedestal or base 1, positioned on the ground which carries a fixed nozzle shield 2 and, a supporting 3,319,7tl1 Patented May 16, 1967 ice plate 3 which is movable in respect to the shield 2. The movable supporting plate 3 and the nozzle shield 2 carry a mold 4. Stringers 7,7, which are connected to the nozzle shield 2 and to a rear shield 6, provide means upon which the movable mold part 3 is slidable.

In accordance with the invention, the pressure casting device includes a shot cylinder 10, having a piston 11 slidable therein. Piston 11 is provided with a piston rod 12 and the latter carries at its outer end a shot piston 13. In accordance with the invention, the piston 11 and the piston rod 12 are made of a light material predominantly a light metal or completely of a light metal material. The shot piston 13 which comes into contact with the melt is made of -a temperature resistant material and is jacked up onto the piston rod.

The shot piston 13 is displaceable in a filling bushing or cylinder member 15 having a filling aperture or opening 16. In the immediate vicinity of the shot unit, that is, the cylinder 16 with the piston 11, a piston accumulater 20 is arranged. As is visible from FIG. 2, the piston 21 of the piston accumulator 20 is also made of a light material predominantly a light metal.

A pressure gas bottle 25 is connected through a stop valve 26 with a gas chamber 27 of a piston accumulator 20. A gas feeding line 28 is connected into the charm ber 27 and it carries a hand operated stop valve 29. The accumulator 20 has a piston 21 slidable therein separating the gas chamber 27 from a chamber 47 containing the hydraulic fluid. A pump 32 is arranged to take suction from the tank 31 and to deliver it through a check valve 33 into the pressure line 34. A maximum pressure valve 35 is connected between the pressure line 34 and a return line 36. A pressure feed line extends from a reversing slide valve 40 to the cylinder 10 and also through a branch and a check valve 46 to the accumulator chamber 47. The check valve 46 is controllable by means such as a solenoid indicated at 48. The interior of the accumulator 20 is divided by means indicated at 21 into the pressure chamber 27 and the pressure chamber 47. An accumulator line extends from the chamber 47 to a stop valve 51, which leads to the return line 36 on the tank 31. A bypass line 56 extends from the forward end of the shot cylinder 10 to the accumulator line 50 and a check valve in this line permits flow in this direction. The return line 56, which connects the cylinder 10, also leads to the reversing slide valve 40 for flow through the return line 58 back to the tank 31.

The device of the invention indicated in FIGS. 1 and 2 operates as follows:

The mold 4 is closed, that is, the movable mold carrying plate 3 is displaced to the right against the nozzle shield 2. The melt to be pressure cast is then charged through the filling aperture 16 into the filling bushing 15. The first movement of the piston 11 and hence of the shot 13 which will be in contact with the melt occurs slowly as the pump 32 hydraulically forces oil into the cylinder 10. While this occurs, the reversing slide valve 40 is shifted from its indicated position to the left in such a manner that a direct connection between the pressure line 34- and the feed line 45 and between the return line 56 and the second tank line 58 is completed.

At a certain time after the initial displacement of the piston 11, the controllable check valve 46 is opened so that the pressure medium stored in the piston accumulator, under high pressure, becomes active directly on the piston 11. The compressed gas in the chamber 27 expands and the hydraulic fluid in the chamber 47 is caused to flow at great speed out of the chamber through the controllable check valve 46 into the cylinder 10 to move the piston 11 to the left at great speed. In the instant of final mold fillin this movement is abruptly checked. Because the mass of the moved piston 11 and of the piston rod 12 is very small, there is very little kinetic energy imparted therein during movement. In addition, because the path from the piston accumulator 20 into the cylinder is very short, there is very little movement of the fluid so that its kinetic energy is not increased materially. In addition, the piston 21 of the piston accumulator 20 is made of a light metal so that despite its rapid movement very little kinetic energy is imparted therein. The total of the imparted energies therefore remains very low and, therefore, there is only a slight shock when the parts are brought to rest. After the shot stroke is completed, the reversing slide valve 40 is returned to the position indicated in the drawings and the pump 32 delivers the pressure medium into the forward zone of the cylinder 10 to move the piston 11 backwardly to the rest position indicated. At the same time, the pump 32 also delivers pressure medium through the check valve 55 into the piston accumulator 20 and charges it up again.

In order to compensate for gas losses on the one hand, and also to render possible an additional charging or new charging after standstill of the piston accumulator with pressure gas, an extraneous gas line 28 is connected to a piston accumulator 20. For the relief of the piston accumulator 20, especially hydraulically, the accumulator line 50 via the stop valve 51 and the tank line 36 into the tank 31. When the stop valve 51 is opened, the pressure medium, that is, the fluid flows back into the tank 31 and the entire hydraulic system can be charged with a gas through the line 28.

In the embodiment indicated in FIG. 3, similar parts are similarly designated with a prime added. In this embodiment, the accumulator 20' is combined directly into the shot unit 10'. This reduces the amount or distance .of travel of the hydraulic fluid and thus of the kinetic energy which will be imparted in the fluid. A dividing wall 61 is defined in the combined cylinder 10, 20' and it defines a valve seat on which is movable a valve element 63 which is controllable by a solenoid 62. A piston 11 with a piston rod 12' is slidable in the cylinder portion 10'. The piston 11' and the piston rod 12 are made of a light metal material. For reversal to the high shot speed with the under actuation of the piston accumulator 20', the piston rod 12 carries a control cam 65 which acts on a control switch 66. A so-called zero stroke pump 70, that is, a pump which is infinitely variable between zero and maximum delivery delivers fluid pressure from the tank 31 to the pressure line 34'. The zero stroke pump 70 is adjusted by an adjusting device 71 which is connected thereto through a line 72 extending to the pressure line 34. The pressure line 34 leads to a reversing slide valve 80 which selectively permits the connection between the pressure line 34 and the return line 56' and the return line 56 and the second tank line 58. A solenoid 81 is provided for adjusting the reversing slide valve 80. The pressure line 34' is connected through a check valve 83 with an overflow valve 85. A line 86 extends from the central hydraulic zone or chamber 47' of the piston accumulator to the overflow valve 85.

The operation of the embodiment of FIG, 3 is as follows:

The zero stroke pump 70 conveys hydraulic fluid from the tank 31' under the pressure adjusted by the maximum pressure valve 35 into the pressure line 34'. The piston 11 is moved to the left for the shot when the control valve 63 is lifted off its seat by the solenoid 62. At first there occurs a low feed speed of the piston 11' and the piston rod 12 and the shot piston 13. At a certain time, the control cam 65 leaves the control switch 66 to cause the closing of the switch and the excitation of the magnetic solenoid 62 to open the control valve 63. When this occurs, the total pressure in the piston accumulator portion 20 becomes operative on the rear of the piston 11 to cause the latter to be shifted at maximum speed in the direction of the injection. At the instance of final mold filling, shot piston 13 and hence also the piston 11' is abruptly stopped. However, since as illustrated in the other embodiments and in the present embodiment, the piston 11 and the piston rod 12' are made of a light weight metal, very little kinetic energy will be stored in these elements. In addition, the path of travel of the fluid from the pressure zone 47 into the zone 9 and the cylinder 10 is very small due to the close association of these parts. Thus, an extremely light impact occurs. After the shot, the reversing slide valve is displaced to the right by the solenoid 81 and the zero stroke pump 70 conveys fluid under pressure as adjusted by the maximum pressure valve 35 through the pressure line 34 and the return line 56 into the cylinder 10 to cause the return movement of the piston 11 with the piston rod 12'. In addition, the maximum pressure becomes operative from the pressure line 34' through the check valve 83 and the reducing valve 85 in the hydraulic zone 47 of the piston accumulator 20. But, due to the reducing valve, the pressure in line 86 is lower than the return line 56. But, since a greater pressure prevails in the side of the cylinder 10 away from the cylinder zone 9 then in the cylinder zone 9 and in the hydraulic zone 47 there results an excess of force so that the piston is moved to the right. At the same time, piston 21 of the piston accumulator 20 is moved to the right so that gas pressure is again built up. Owing to the simultaneous feeding of the hydraulic fluid both into the front zone of the shot cylinder 10 as well as into the intermediate hydraulic zone 47 a leakage loss compensation takes place. Therefore, the necessary oil is always present in the hydraulic zones.

The apparatus arrangement is characterized by radical reduction of the masses imparting kinetic energy. This reduction of the kinetic energies, however, automatically brings about a reduction of the impacts also upon sudden stopping. Since the objects of the present invention are not the hydraulic arrangements, but essentially the reduction of the kinetic energies, details of the hydraulic arrangements are dispensed with in some instances although it is within the scope of the invention that refinements of such details can be installed.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A pressure casting device comprising, means defining a mold, a bushing connected to said mold for filling the mold with a charge of material to be cast, a shot piston displaceable in said bushing for directing the charge of material into the mold under pressure, a cylinder, a partition in said cylinder dividing the same into a pressure cylinder section and an accumulator cylinder section, a pressure piston slidable in said pressure cylinder section and connected to said shot piston for displacing said shot piston in said bushing, means for directing fluid under pressure to said cylinder including a pump connected to said cylinder for creating a pressure differential on said pressure piston to effect initial movement of said shot piston for injecting a material to be cast into said mold, normally closed valve means in said partition, an accumulator piston in said accumulator cylinder section, and pressure means biasing said accumulator piston toward said partition, said pump supplying fluid under relatively high pressure to said accumulator cylinder section between said accumulator piston and said partition, and said valve means opening slightly, during such initial movement, said valve means opening fully after said initial movement has taken place to apply said relatively high pressure to said pressure cylinder section to effect rapid movement of said shot piston after an initial movement has taken place, at least said shot piston being made of a relatively light material.

2. A pressure casting device comprising, means defining a mold, a bushing connected to said mold for filling the mold With a charge of material to be cast, a shot piston displacea'ble in said bushing for directing the charge of material into the mold under pressure, a pressure cyi inder, a pressure piston slidable in said pressure cylinder and connected to said shot piston for displacing said shot piston in said bushing, means for directing fluid under pressure to said pressure cylinder including a pump connected to said pressure cylinder for directing an initial flow of relatively low fluid pressure behind said pressure piston during the initial movement of said shot piston for injecting a material to be cast into said mold and a fluid pressure accumulator connected to said pressure cylinder and located in close proximity to said pressure cylinder for supplying fluid under higher pressure than said pump, a short conduit connecting said accumulator to said pressure cylinder for directing pressure to effect rapid movement of said shot piston after an initial movement has taken place, at least said shot piston being made of a relatively light material so that the kinetic energy imparted thereto during movement Will be relatively small, said accumulator having a piston slidable therein and dividing said chamber into a gas chamber and a liquid chamber, and means for charging said gas chamber with a pressurized gas, said liquid chamber being connected to said pressure piston.

3. A pressure casting device comprising, means defining a mold, a bushing connected to said mold for filling the mold With a charge of material to be cast, a shot piston displaceable in said bushing for directing the charge of material into the mold under pressure, a pressure cylinder, a pressure piston slidable in said pressure cylinder and connected to said shot piston for displacing said shot piston in said bushing, and means for directing fluid under pressure to said pressure cylinder including a pump connected to said pressure cylinder for directing an initial flow of relatively low fluid pressure behind said pressure piston during the initial movement of said shot piston for injecting a material to be cast into said mold and a fluid pressure accumulator connected to said pressure cylinder and located in close proximity to said pressure cylinder for supplying fluid under higher pressure than said pump, a short conduit connecting said accumulator to said pressure cylinder for directing pressure to effect rapid movement of said shot piston after an initial movement has taken place, at least said shot piston being made of a relatively light material so that the kinetic energy imparted thereto during movement Will be relatively small, at least said shot piston and said pressure piston being made of a light Weight metal material, said accumulator having an accumulator piston slidable therein and dividing said accumulator into a gas pressure chamber and a fluid pressure chamber, said piston being slidable in accordance with the magnitude of the gas pressure and fluid pressure therein.

References Cited by the Examiner UNITED STATES PATENTS 2,182,059 12/1939 Schwartz 22-68 2,862,266 12/1958 Peras 2268 2,893,082 7/1959 Hodler 22-69 X 2,896,279 7/1959 Nyselius 2268 I. SPENCER OVERHOLSER, Primary Examiner,

E. MAR, Assistant Examiner, 

2. A PRESSURE CASTING DEVICE COMPRISING, MEANS DEFINING A MOLD, A BUSHING CONNECTED TO SAID MOLD FOR FILLING THE MOLD WITH A CHARGE OF MATERIAL TO BE CAST, A SHOT PISTON DISPLACEABLE IN SAID BUSHING FOR DIRECTING THE CHARGE OF MATERIAL INTO THE MOLD UNDER PRESSURE, A PRESSURE CYLINDER, A PRESSURE PISTON SLIDABLE IN SAID PRESSURE CYLINDER AND CONNECTED TO SAID SHOT PISTON FOR DISPLACING SAID SHOT PISTON IN SAID BUSHING, MEANS FOR DIRECTING FLUID UNDER PRESSURE TO SAID PRESSURE CYLINDER INCLUDING A PUMP CONNECTED TO SAID PRESSURE CYLINDER FOR DIRECTING AN INITIAL FLOW OF RELATIVELY LOW FLUID PRESSURE BEHIND SAID PRESSURE PISTON DURING THE INITIAL MOVEMENT OF SAID SHOT PISTON FOR INJECTING A MATERIAL TO BE CAST INTO SAID MOLD AND A FLUID PRESSURE ACCUMULATOR CONNECTED TO SAID PRESSURE CYLINDER AND LOCATED IN CLOSE PROXIMITY TO SAID PRESSURE CYLINDER FOR SUPPLYING FLUID UNDER HIGHER PRESSURE THAN SAID PUMP, A SHORT CONDUIT CONNECTING SAID ACCUMULATOR TO SAID PRESSURE CYLINDER FOR DIRECTING PRESSURE TO EFFECT RAPID MOVEMENT OF SAID SHOT PISTON AFTER AN INITIAL MOVEMENT HAS TAKEN PLACE, AT LEAST SAID SHOT PISTON BEING MADE OF A RELATIVELY LIGHT MATERIAL SO THAT THE KINETIC ENERGY IMPARTED THERETO DURING MOVEMENT WILL BE RELATIVELY SMALL, SAID ACCUMULATOR HAVING A PISTON SLIDABLE THEREIN AND DIVIDING SAID CHAMBER INTO A GAS CHAMBER AND A LIQUID CHAMBER, AND MEANS FOR CHARGING SAID GAS CHAMBER WITH A PRESSURIZED GAS, SAID LIQUID CHAMBER BEING CONNECTED TO SAID PRESSURE PISTON. 